Work machine

Abstract

An object of the present invention is to provide a work machine that can increase the operation speed of an actuator by a regenerating function while ensuring accuracy of position control of the actuator. For this purpose, a controller computes a target actuator supply flow rate by subtracting a regeneration flow rate from a target actuator flow rate, computes a target flow control valve opening amount on the basis of the target actuator supply flow rate, computes a target pump flow rate equal to or more than the sum of a plurality of the target actuator supply flow rates, controls flow control valves according to the target flow control valve opening amount, and controls a hydraulic pump according to the target pump flow rate.

The invention claimed is: 
     
       1. A work machine comprising:
 a machine body; 
 a work device attached to the machine body; 
 actuators that drive the machine body or the work device; 
 a hydraulic operating fluid tank; 
 a hydraulic pump that sucks hydraulic fluid from the hydraulic operating fluid tank and supplies the hydraulic fluid to a corresponding one of the actuators; 
 flow control valves that are connected in parallel to a delivery line of the hydraulic pump and control a flow of the hydraulic fluid to be supplied from the hydraulic pump to the corresponding one of the actuators; 
 control levers for giving instructions for operation of the actuators; and 
 a controller that controls the flow control valves according to operation instruction amounts from the control levers, wherein: 
 the work machine includes:
 a regeneration valve disposed on a hydraulic fluid line that connects a meter-out port and a meter-in port of one of the flow control valves to each other, and 
 a pressure sensor that senses a differential pressure across the regeneration valve, and 
 
 the controller is configured to:
 for each of the actuators, compute a target actuator flow rate based on the operation instruction amounts from the control levers, 
 compute a regeneration flow rate of hydraulic fluid passing through the regeneration valve based on the differential pressure across the regeneration valve, 
 compute target actuator supply flow rates by subtracting the regeneration flow rate from each of the target actuator flow rates, 
 compute target flow control valve opening amounts based on the target actuator supply flow rates, 
 compute a target pump flow rate equal to or more than a sum of the target actuator supply flow rates, 
 control the flow control valves according to the target flow control valve opening amounts, and 
 control the hydraulic pump according to the target pump flow rate. 
 
 
     
     
       2. The work machine according to  claim 1 , wherein:
 the flow control valves include:
 directional control valves that control directions of the hydraulic fluid to be supplied from the hydraulic pump to the actuators, and 
 auxiliary flow control valves that limit flow rates of hydraulic fluid to be supplied from the hydraulic pump to meter-in ports of the directional control valves; and 
 
 the regeneration valve is disposed on a hydraulic fluid line that connects the meter-out port and the meter-in port of a directional control valve among the directional control valves that corresponds to the one of the flow control valves. 
 
     
     
       3. The work machine according to  claim 1 , wherein:
 the flow control valves are directional control valves that control directions and flow rates of the hydraulic fluid to be supplied from the hydraulic pump to the actuators, and 
 the regeneration valve is disposed within a spool of a directional control valve among the directional control valves that corresponds to the one of the flow control valves. 
 
     
     
       4. The work machine according to  claim 1 , including:
 a variable restrictor valve disposed on a hydraulic fluid line that connects the meter-out port of the one of the flow control valves and the hydraulic fluid tank to each other, wherein 
 the controller is configured to, in a case where the regeneration flow rate exceeds the target actuator flow rate of an actuator among the actuators that corresponds to the one of the flow control valves, increase an opening amount of the variable restrictor valve until the regeneration flow rate becomes equal to or lower than the target actuator flow rate among the target actuator flow rates that corresponds to the one of the flow control valves. 
 
     
     
       5. The work machine according to  claim 1 , including:
 an automatic control function selector switch that gives an instruction for enabling or disabling an automatic control function of the machine body or the work device, wherein 
 the controller is configured to, in a case where the automatic control function selector switch gives an instruction for disabling the automatic control function, compute the target flow control valve opening amounts and the target pump flow rate based on the operation instruction amounts from the control levers.